The present invention relates to a method of applying dyeliquor or other treating compositions to stationary or running substrates of fibrous material or the like, such as continuous webs or discrete sections or panels of carpeting, paper, cords, strips, filaments and the like. More particularly, the invention relates to improvements in a method of applying foamed treating compositions to substrates through the interstices of a screen.
German Offenlegungsschrift No. 25 23 062 discloses an apparatus which can be utilizied for the application of a foamed treating composition to a stationary or moving substrate. The apparatus of this German publication embodies a foam generator and further includes means for applying a single type of foamed treating composition directly to the substrate. A drawback of such apparatus is its lack of versatility, due in part to the provision of a single foam generator, and its inability to provide the substrate with a predictable coating of treating composition. Direct application of a foam onto a stationary or running substrate presents many serious problems and is highly unlikely to result in uniform application of the foamed treating composition.
German Pat. No. 20 26 492 discloses the application of a liquid treating composition to a substrate through the interstices of a screen. This prior publication does not contain any suggestion to employ a foamed treating composition which exhibits a number of important advantages, especially during transport from the foam generator all the way to or into immediate or close proximity of the locus of application to the substrate.
German Auslegeschrift No. 22 14 377 discloses an apparatus which can be used to apply two or more miscible or unmiscible foamed treating compositions to a substrate so as to provide the latter with a multicolored pattern. The application of foamed compositions takes place directly onto the substrate with the aforediscussed drawbacks as concerns the uniformity and/or predictability of distribution of the treating composition.
It has been found that none of the aforediscussed prior proposals satisfy strict requirements regarding the reproducibility and accuracy of the application of dyeliquors and/or other treating compositions to stationary or running substrates, for example, to the naps of carpets, in such a way that the base layer of the treated material is not soaked with the liquid but that the entire nap is properly dyed all the way to its very roots. Moreover, the aforediscussed conventional apparatus are incapable of predictably applying two or more different dyes at a single dye-applying station and with a single applicator. Still further, heretofore known apparatus and methods do not allow for a wide selection of various treating compositions and/or patterns to be applied to the substrate. Reproducibility of the application of two or more different treating compositions or two or more different shades of a given treating composition is important not only when the substrate is in motion but perhaps even more when the application of treating compositions takes place in successive stages with an interruption for shifting of the substrate between successive stages. Last but not least, heretofore known proposals do not allow for rapid and inexpensive conversion or shifting from operation in accordance with a predetermined pattern to rapport-free application of dyes to successive unit lengths or areas of a substrate or vice versa.
Attempts to overcome the aforediscussed drawbacks of heretofore known apparatus for the application of one or more treating compositions to moving or stationary substrates include resort to an entirely different mode of operation, namely, the utilization of a large number of nozzles which are actuated to spray different types of liquid treating compositions (e.g., differently colored dyes) onto the nap of a carpet or the like. It has been found that such proposals also fail to meet exacting requirements concerning the accuracy and reproducibility of the patterns (and especially the establishment of clear boundaries between differently colored sections of the patterns), even of the nozzles are caused to discharge sprays of treating composition at a time when their orifices are held in immediate proximity of the substrate. This is due to the fact that the sprays which issue from such orifices cannot be controlled and adjusted with a very high or highest degree of accuracy. Moreover, the sprays are likely to soak the substrate, i.e., to moisten not only the parts (such as the nap of a carpet) which are to be dyed but also those parts which should not be contacted by the treating composition at all. This is due to the fact that the rate of discharge of atomized liquid at the center of the cone which issues from the orifice of a nozzle is higher than the rate of discharge along the marginal portions of the cone; therefore, and if the marginal portions of the cone should supply atomized liquid treating composition at a rather pronounced rate, the admission of liquid in the central region of the cone is invariably excessive.
The presently known teachniques of applying one or more treating compositions to the nap of a carpet or the like exhibit many additional drawbacks. Thus, a pattern of certain size normally repeats itself all over along the length of the substrate, and the size of each such pattern is invariably the same. This can present problems and can entail waste in the material of the carpet when the latter is to be laid and the area to be covered is such that it is necessary to resort to a patchwork of two or more pieces of carpeting. Care should be taken to avoid the presence of clear-cut boundaries between the neighboring pieces. As mentioned above, heretofore known proposals fail to provide an acceptable solution of such problems.
An additional problem which cannot be overcome by resort to presently known methods and apparatus is that they do not allow to maintain a specific color unchanged for the application of a long piece of substrate. The sections which are dyed with successively mixed or otherwise formed treating compositions exhibit different shades, tones or other color qualities and the differences in shading can be quite pronounced so that it is not possible to match two pieces which have been dyed during different stages of the coloring operation.